Flexible conduit.



U. s. ARMSTRONG.

FLEXIBLE 'GONDUITV APPLICATION FILED AUG. 8. 1910.

Patented July 25, 1911 'f;:r,i. B a. v

w s? m/M ULYSSES S. ARMSTRONG, OF NEW KENSINGTON. PENNSYLVANIA.

FLEXIBLE CONDUIT.

Specification of Letters Patent.

Patented July 25, 1911.

Application filed August 8, 1910. Serial No. 576,155.

v declare the following to be a full, clear, and

exact description of the invention, such as will enable others skilled in the art to which it RPPel'tfllIls to make and use the same.

My invention relates to improvements in flexible conduits and more particularly to ilexiblc -.teel tubing for electrical conductors and for analogous conduit purposes.

The principal object of this invention is to provide a flexible metal tubing or con duit having an interior free from concave surfaces and projections so that wires or conductors may be easily fished or placed in the conduit at a very small expense.

Another object of the invention is to'provide a ilcxiblc conduit of this character having improved means whereby the o'iiferent strips or layers of which it is composed will be interlocked or held in engagement and prevented from separating when the conduit llexed or when there is longitudinal strain on the onduit.

With the above and other objects in view thc invention resides in the combination and arrangement of parts and details of construction hcreinat er fully described and claimed and illustrated in the accon'ipanying drawing in which:

l igurc l is a side elevation of a portion of a llexiblc conduit embodying my inven tion. Fig. 2 isa longitudinalsection through the same. Figs. 3, 4 and 5 are detail perspu ive views of the three strips or layers composing the tubing or conduit shown in 1 and 2. Fig. l) is a detail longitudinal fiiltilull through a slightly modified form of the invention.

ln the 'n'cterred embodiment of my invcntion which I have illustrated in Figs. 1 to 5 inclusive, the conduit is composed of tlircc spirally twisted or coiled strips 1. 2 and 5 arranged so that they overlap. The inner st rip or layer 1 is composed of a llat strip oi stccl or other suitable material bent into spiral form so that there are slight spaces bctwccn its coils as shown in Fig. 2. lly making this inncr member 1 from a ilat strip i will be noted that. the interior of the conduit will be free from concave recesses or depressions and inwardly extending projections, commonly found in conduits of this character now on the market and consequently electrical wires or conductors can be quickly and easily inserted through the conduit. The intermediate strip 2 may be of fiber or any other material which will permit said strip to serve as'a gasket and also, if desired, as a locking member. As illustrated in Figs. 1 and 2 the strip or member 2 is made of flat material and spirally twisted so as to extend across the spaces t between the coils of the strip or member 1. To permit this strip or gasket 2 to serve as a locking member it is formed at intc vals along its edges with openings 5 adapted to receive tongues (3 projecting outward from the strip 1. By interlocking the strips or members i and 2 in this manner it will be seen that the device will be greatly strengthened and prevented iron'i being pulled open when there is any st -ain in a longitudinal direction upon it, and at the same time the flexibility of the conduit is not in any way impaired. The outer strip or member 3 is made from a strip of steel or other metal oi scmi-oval or concave shape in cross section and it is adapted to overlap the g shot or strip 2 and consequently the spaces t between the coils of v the inner strip or layer 1.

The concave shape ot the outer strip or member 3 is such that it not only protects the gaskct 2 but also scrvcs the additional purpose of a. locking member. Since the projections or i'astcncrs (3 project into ongagcmcnt with the concave inner face oi. the strip 3 they prevent the longitudinal scparation of the coils of thc strip 1. in this cou ncction it will be noted that the gasket or intcrincdiatc strip 2 may be oinittcd cntircly and the lockingtongucs or projections t made to co-act with the inncr concave suriacc oi thc outer strip 1 it will be further notcd that, if desired, the locking tcllgu (3 m y co-act or engage with the concave inucr surt'acc of the strip 3 and a round or oval shapc gasket 7 may be arranged ovcr the spaces between the coils oi the strip 1 as shown in Fig. (i of the drawing. ()n rcierring to this figure it will be obscrvcd that the gaskct. T is arranged between the tongues or projections (3 but is not slotted or rcccsscd for ongagcmcnt with such projections and consequently it serves merely as a gasket and not as a combined gasket and locking member as in the form of the invention first described.

The strips or layers of the conduit may be of the material as above noted although the inner and outer strips are preferably formed from steel or other metal and when so -:tormed they are preferably galvanized,

tinned, or lead coated.

From the foregoing it will be noted that my invention provides an exceedingly simple and practical conduit or tubing having an unobstructed bore or race-way through which electric Wires or conductors may be easily passed, and While the invention has been particularly shown and described as embodied in a tubular conduit, I wish it understood that it may be used as an armour covering for electric Wires. It will be furthernoted that the peculiar construction of the device renders the conduit or covering exceedingly strong without detracting from its flexibility and that when longitudinal strain is placed upon the device there will be no danger of the layers being pulled apart.

I claim:

A device of the character set forth comprising inner and outer spirally twisted strips, the inner strip being formed from flat material and the outer strip being formed from material of concave shape in cross section and being arranged to extend over the spaces of the coils of the inner strip, locking tongues struck up from the coils of the inner strip and adapted to engage the concave inner faces of the coils of the outer strip, and an intermediate spirally coiled gasket strip arranged within the outer strip and extending over tliespace of the coils of the inner strip, said gasket being formed with slots to receive said tongues whereby te serve to lock the adjacent coils of the inner strip.

In testimony whereof I have hereunto set my band 111 presence of two subscribing witnesses.

ULYSSES S. ARMSTRONG. \Vitnesses:

B. R. KLINE, H. S. MILLER. 

